1. Field of Invention
The present invention relates to improved bolted-on automotive gasket assemblies for internal combustion engines, and more particularly to improved gaskets applied between the bottom flange portions of such engines and the oil pan structures secured thereto.
2. Description of the Prior Art
Those skilled in the art will appreciate the difficulty of maintaining a good quality oil seal between the bottom flange of an internal combustion engine and the oil pan secured to the flange. Typically, the pan is secured to a flange which has portions in various planes, some of the portions including semi-cylindrical sealing surfaces, such as, for example, the portion situated at the centrally located rear main bearing cap of the typical vehicle. Indeed, most oil pan covers have two generally longitudinally extending flat flange surfaces which mate with engine mounting flanges, and two generally semi-circular recessed ends adapted to accommodate the bearing cap and the timing chamber cover, respectively. Thus, the overall environment for sealing oil pan structures is difficult at best.
Unitary prior art molded rubber gaskets have been employed to seal such described irregular boundary sealing criteria. However, such gaskets generally have main body portions defining bolt or fastener apertures and include concave ends for sealing the noted semi-circular recessed ends. Such gaskets are also difficult to install to the extent that they are limp; i.e. without stiffness. Such gaskets are also prone to splitting problems at the fastener holes.
As a result, traditional gaskets employed to seal such areas have been subject to considerable redesign efforts in recent years, particularly for aftermarket replacements. One replacement application is directed to identifying a suitable substitution for an original equipment gasket consisting of a cork material. Gasket materials suggested as replacements have included thermoset or thermoplastic elastomers, or possibly even soft plastic resins, such as unfilled nylon. In any event, the seal must be robust enough to avoid premature deterioration, and must be resilient enough to seal areas that may be quite narrow. In addition, upon premature failure of the main seal, some attention is needed to provide a backup seal in or around the bolthole apertures of the gasket, a recognized source of potential secondary leakage.
The present invention is an improved boundary gasket for sealing between flanged portions of axially mated rigid surfaces. A unitary molded rubber gasket incorporates a rigid metallic carrier, and is thus adapted for sealing between flanged portions between the bottom of an engine block and an associated engine oil pan secured thereto. In one preferred form, the gasket has a generally rectilinearly shaped body, and includes a one-piece circumferentially extending rigid metallic carrier having a first axial thickness. The carrier, which acts as a bolt crush limiter, is adhesively bonded to a one-piece elastomeric sealing body; the sealing body is bonded to the metallic carrier at the radially innermost edge of the carrier. The carrier thus also imparts stiffness to the sealing body, which includes a plurality of spaced elastomeric apertures adapted for accommodating passage of bolt members for fastening the flanged portions of engine and oil pan together about the gasket body. The apertures are designed for sealing against secondary leakage of fluids (e.g., oil) between said apertures and said bolt members.
For this purpose, each aperture includes at least two axially spaced integral sealing lips, the lips extending radially inwardly from the aperture wall for sealingly engaging an associated bolt member. The elastomeric sealing body further includes a unitary sealing bead integral with, and extending circumferentially about, said sealing body, the bead positioned radially outwardly of the spaced apertures for providing a primary sealing function. The bead has a second axial thickness greater than the first; thus upon the tightening of the bolt members the elastomeric material of the bead will only be crushed or compressed to the limiting axial thickness of the carrier.
Finally, the same preferred embodiment of the gasket has two longitudinally extending, flat, side portions, with arcuate end portions contiguously joining the side portions for accommodating semi-circular members situated immediately adjacent the oil pan.